Double your muffness, double your fun

[Mark Hammer]

Somewhere in 1972 or so, I was playing in a band with borrowed equipment.  One evening I was loaned two EHX Muff Fuzz units, of the sort that you plugged directly into the guitar (see video).  I plugged them in series, and the fuzz seemed to be neverending.  I imagine the cinderblock construction of the school gym we were playing in had an impact on the apparent sustain.  BUt echoes aside, I kinda liked it.

So when EHX released the Double MUff, my thought was "Awright!".  The stock unit has a pair of near identical Muff Fuzzes, with the first one just a smidgen different, so as to produce a slightly rounder tone.  Underneath, the Muff Fuzz is really a silicon Fuzz Face, with fixed gain, and a back-to-back diode pair on the output, such that the fuzz comes partly from the diodes and not entirely from the FF circuit.  It has a level control for each of the two Muffs included, and you can either take your output from the first one, or from the second one (with the first one driving it).  How hard you push the second one depends on the output setting of the first one.  So, between two knobs and a slide switch, there is a lot of variation.

Not content with the stock arrangement, I decided to build one with some extra bells and whistles.  Below is the stock circuit, and my modded one.  The BC550 transistors I had measured around hfe-360 or so, so I used a BC546 (hfe = 270) for Q1 and BC550 for Q2 in each Muff half.  I made a couple of changes to add a little more variety.

• I added a Gain control, by placing a 10k pot and 10uf cap in parallel with the emitter 3k3 resistor in the first Muff.  Reducing the pot resistance adds some serious sizzle.
• I added a 10k variable clipping pot between the diode pair and ground in Muff 1.  Reducing the clipping and going to stock gain yields a grunting tone, rather than sizzle.  Diming the gain and tying the diodes directly to ground yields serious sizzle.
• Because I could get all the sizzle I wanted out of Muff 1, I removed the diodes entirely from MUff 2.  IN their place is a 3-position tone switch to provide two degrees of treble cut on top of stock tone.  Cap values TBD
• After my experience with the ZVEx Wooly Mammoth, and adding more feedback resistance to the same path in a couple of Jen Fuzz builds, I added a 120k resistor in series with the stock 100k feedback in Muff 2.  Increasing the feedback resistance induces a degree of "glitchiness", that I suppose will appeal to Devi Ever and Dwarfcraft fans.  I may increase it to 150k.

A lot of tonal variety, from relatively mild overdrive to make-it-stop sustaining searing fuzz.  Being able to shape the tone of Muff 1 to alter how MUff 2 is driven is a neat trick.  IF you find one of the EHX units cheap, it's definitely worth picking up to mod.

[Plexi]

Nice story behind, Mark!

[Plexi]

Bump for some idea:
judging for the design, I asume the clipping diodes have a huge influence in the sound.
I'll try a 500k pot as voltage divider, selecting between bypass (or germanium/silicon/LED) and diodes.

[Plexi]

Hey Mark..!
Can you please re-upload the photo-@#$%it down pics? 

I don't wanna lie: it have too much less distortion of what I expected.
Now I understand why the need of use two.